Sources of illiquidity and their costs
Illiquidity has several distinct dimensions. Bid-ask spread: the cost of entering and exiting immediately, borne by investors who trade. Small-cap stocks and corporate bonds carry spreads of 50–200bps; liquid large-cap equities carry 1–5bps. Market impact: for large trades, the act of buying or selling moves the price against you — institutional investors in small or mid-cap stocks can drive up the price simply by their own purchase. Price discovery: illiquid assets’ prices are not continuously updated — real estate values are appraised quarterly; private equity valuations are updated sporadically, creating an artificial smoothing of volatility that understates true risk. Lock-up periods: private equity and hedge funds impose lock-ups (1–10 years) during which capital cannot be withdrawn regardless of performance — investors require compensation for surrendering this optionality.
The illusion of private market stability
One subtle aspect of the liquidity premium: illiquid assets appear less volatile than they actually are, because their prices are not continuously marked-to-market. Private equity funds report quarterly NAVs that are smoothed by appraisal-based valuations — their correlation with public equity markets appears low, and their Sharpe ratios appear high. But this is partly an artefact of stale pricing. When forced liquidations occur (LP selling, secondary market transactions), private asset prices show correlations with public markets that are much higher than the reported numbers suggest — particularly in crises, when liquidity premium becomes most costly to bear. The Yale Endowment model (heavy alternatives allocation) has generated strong returns, but its success is partly attributable to extraordinary deal access and manager selection rather than liquidity premium alone.
“The liquidity premium is real — but you only earn it by committing to hold through the periods when you most desperately want to sell.”
What this means for you
For investors who genuinely have long investment horizons and no need to liquidate — university endowments, pension funds with long-dated liabilities, wealthy individuals — accepting illiquidity is rational and the premium is earnable. For most individual investors, however, the liquidity premium in private markets is partly offset by manager fees, and the risk of needing liquidity during a crisis is systematically underestimated. The most accessible form of the liquidity premium for retail investors is through small-cap equities and less liquid bond segments — where the liquidity premium is real but the assets trade daily. Understanding that some of any fund’s apparent "alpha" may be unlabelled liquidity premium (compensation for bearing illiquidity risk that doesn’t show up in measured volatility) is essential to evaluating alternative investment propositions.